Taking advantage of newer aggregation operators if you have upgraded your MongoDB server. For example, MongoDB 3.4 added manynew aggregation stages and expressionsincluding support for working with arrays, strings, and facets. There are also a number ofAggregation Pipeline Optimizationsthat automatically...
The QO enables only the shard-level aggregation instead of file-level aggregation. In this case, you can set the following GUC parameter to on to perform multi-phase HashAggregate. If the SQL statement already uses a multi-phase aggregate, no additional adjustments are required. SET optimizer...
db.example.aggregate([{$match:{someFlag:true} } ] ) The field is only present if the value istrueand only applies to explain on aggregation pipeline operations. Whentrue, because the pipeline was optimized away, no aggregation stage information appears in the output. ...
AGGREGATION:Operators and steps used for queries that involve aggregate functions and GROUP BY operations. AggregateaggrOperator/step for scalar aggregate functions. HashAggregateaggrOperator/step for grouped aggregate functions. Can operate from disk by virtue of hash table spilling to disk. ...
Starting in MongoDB 4.2, you cannot run theexplaincommand/db.collection.explain()inexecutionStatsmode orallPlansExecutionmode for anaggregation pipelinethat contains the$outstage. Instead, you can either: run the explain inqueryPlannermode or
Benefrancis / system-design-101 Public forked from ByteByteGoHq/system-design-101 Notifications You must be signed in to change notification settings Fork 0 Star 0 Explain complex systems using visuals and simple terms. Help you prepare for system design interviews. ...
从这个worker第一次Entry to this plan node时间到返回这个NODE的最后一条有效tuple,(seg9) with 2669 ms to end-- 从query dispatcher(QD)发起,到返回这个NODE的第一条有效tuple,start offset by 595 ms.Rows out: Avg118.2rows x41workersatdestination. Max192rows (seg9)with2669mstoend,startoffsetby595...
DFEPipelineScan – Scans the database for the given pattern argument, with or without a given filter on column(s). DFEProject – Takes multiple input columns and projects only the desired columns. DFEReduce – Performs the specified aggregation function on specified variables. ...
In Stage-1 for example, the Reducer Operator Tree is carrying out a partial aggregation where as the Reducer Operator Tree in Stage-2 computes the final aggregation from the partial aggregates computed in Stage-1 The use of DEPENDENCY in the EXPLAIN statement produces extra information about the...
IndexRangeScan: Index scans with the specified range. TiDB aggregates the data or calculation results scanned from TiKV/TiFlash. The data aggregation operators can be divided into the following categories: TableReader: Aggregates the data obtained by the underlying operators like TableFullScan or Tab...